Aspects described herein relate generally to lighting devices, and more particularly to ballast circuitry for discharge lamps.
When designing lamps and associated circuitry, economic considerations are of paramount importance and often mean the difference between an acceptable design and an optimal design. Often, one or more of lamp size, manufacture cost, and/or energy efficiency dictate a majority of parameters associated with a given lamp design. Modern lamps come in a variety of sizes to accommodate multiple design variations. For instance, a T8 lamp size is approximately one inch in diameter, while a T12 lamp is approximately one and a half inches in diameter. Other sizes are also available to meet designer and consumer needs.
A gas discharge lamp is one example of what is known as a “negative resistance” device, which is a device that is capable of drawing an increasing amount of current until it either burns out the power source or itself. Often, such discharge lamps employ a ballast to control an amount of current flowing through a lamp circuit. A ballast may be as simple as resistor in series with a lamp, such as is utilized for the relatively low-powered neon lamp. More complex ballasts may be utilized for higher power applications, and may comprise resonant components such as capacitor and inductors. Typically, a reactive ballast is more efficient than a simple resistor.
Electronic ballasts utilize electronic circuitry to stabilize current for fluorescent lamps, high-intensity discharge lamps, and the like. Electronic ballasts may be started using one of several starting techniques, including “instant” start, “rapid” start, and “programmed” start. The instant start starts a lamp in the short term, because it starts and operates the ballast without preheating a cathode associated therewith, which results in low energy cost to start but wears out the lamp more rapidly than other starting protocols due to the violent nature of the starting method. The rapid starting technique starts the ballast and heats the cathode concurrently, resulting in a relatively long start time while mitigating the deleterious effects of a cold start on the lamp's cathode. Finally, the programmed start technique employs a cathode preheating period at low glow discharge current which increases the lamp's life for frequency switching applications.
With regard to energy efficiency, a lamp and/or ballast may be designed to minimize power losses as well as to effectively minimize power consumed by the lamp and/or ballast. In the case of manufacturing cost, it may be desirable to minimize a number of circuit components needed to perform a given function, as well as to design circuits such that perform a given function using a number of least-expensive parts and to avoid costly components such as integrated circuits and the like. With respect to ballast size, it may be desirable to design a circuit that occupies as little space as possible to perform the given function in order to facilitate utilization of the ballast in applications where space conservation is an issue. There is an unmet need in the art for systems and/or methods that facilitate overcoming deficiencies associated with the foregoing.